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Enhancements to the code generator for the IN operator that result in much

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faster queries in some cases, for example when the RHS of the IN operator
changes for each row of a large table scan.

FossilOrigin-Name: 436e884215e2b33ca3fbb555362237b12827c07a
This commit is contained in:
drh
2014-08-02 21:03:33 +00:00
parent 16d511a664
commit bb53ecb1db
6 changed files with 165 additions and 69 deletions
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src/expr.c
+141 -54
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@@ -1491,6 +1491,24 @@ static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
sqlite3VdbeJumpHere(v, j1);
}
#ifndef SQLITE_OMIT_SUBQUERY
/*
** The argument is an IN operator with a list (not a subquery) on the
** right-hand side. Return TRUE if that list is constant.
*/
static int sqlite3InRhsIsConstant(Expr *pIn){
Expr *pLHS;
int res;
assert( !ExprHasProperty(pIn, EP_xIsSelect) );
pLHS = pIn->pLeft;
pIn->pLeft = 0;
res = sqlite3ExprIsConstant(pIn);
pIn->pLeft = pLHS;
return res;
}
#endif
/*
** This function is used by the implementation of the IN (...) operator.
** The pX parameter is the expression on the RHS of the IN operator, which
@@ -1510,6 +1528,8 @@ static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
** IN_INDEX_INDEX_DESC - The cursor was opened on a descending index.
** IN_INDEX_EPH - The cursor was opened on a specially created and
** populated epheremal table.
** IN_INDEX_NOOP - No cursor was allocated. The IN operator must be
** implemented as a sequence of comparisons.
**
** An existing b-tree might be used if the RHS expression pX is a simple
** subquery such as:
@@ -1539,6 +1559,13 @@ static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
** be used unless <column> is an INTEGER PRIMARY KEY or an index can
** be found with <column> as its left-most column.
**
** If the IN_INDEX_NOOP_OK and IN_INDEX_MEMBERSHIP are both set and
** if the RHS of the IN operator is a list (not a subquery) then this
** routine might decide that creating an ephemeral b-tree for membership
** testing is too expensive and return IN_INDEX_NOOP. In that case, the
** calling routine should implement the IN operator using a sequence
** of Eq or Ne comparison operations.
**
** When the b-tree is being used for membership tests, the calling function
** might need to know whether or not the RHS side of the IN operator
** contains a NULL. If prRhsHasNull is not a NULL pointer and
@@ -1637,6 +1664,22 @@ int sqlite3FindInIndex(Parse *pParse, Expr *pX, u32 inFlags, int *prRhsHasNull){
}
}
/* If no preexisting index is available for the IN clause
** and IN_INDEX_NOOP is an allowed reply
** and the RHS of the IN operator is a list, not a subquery
** and the RHS is not contant or has two or fewer terms,
** then it is not worth creating an ephermeral table to evaluate
** the IN operator so return IN_INDEX_NOOP.
*/
if( eType==0
&& (inFlags & IN_INDEX_NOOP_OK)
&& !ExprHasProperty(pX, EP_xIsSelect)
&& (!sqlite3InRhsIsConstant(pX) || pX->x.pList->nExpr<=2)
){
eType = IN_INDEX_NOOP;
}
if( eType==0 ){
/* Could not find an existing table or index to use as the RHS b-tree.
** We will have to generate an ephemeral table to do the job.
@@ -1935,7 +1978,8 @@ static void sqlite3ExprCodeIN(
v = pParse->pVdbe;
assert( v!=0 ); /* OOM detected prior to this routine */
VdbeNoopComment((v, "begin IN expr"));
eType = sqlite3FindInIndex(pParse, pExpr, IN_INDEX_MEMBERSHIP,
eType = sqlite3FindInIndex(pParse, pExpr,
IN_INDEX_MEMBERSHIP | IN_INDEX_NOOP_OK,
destIfFalse==destIfNull ? 0 : &rRhsHasNull);
/* Figure out the affinity to use to create a key from the results
@@ -1950,68 +1994,111 @@ static void sqlite3ExprCodeIN(
r1 = sqlite3GetTempReg(pParse);
sqlite3ExprCode(pParse, pExpr->pLeft, r1);
/* If the LHS is NULL, then the result is either false or NULL depending
** on whether the RHS is empty or not, respectively.
/* If sqlite3FindInIndex() did not find or create an index that is
** suitable for evaluating the IN operator, then evaluate using a
** sequence of comparisons.
*/
if( destIfNull==destIfFalse ){
/* Shortcut for the common case where the false and NULL outcomes are
** the same. */
if( eType==IN_INDEX_NOOP ){
ExprList *pList = pExpr->x.pList;
CollSeq *pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
int labelOk = sqlite3VdbeMakeLabel(v);
int r2, regToFree;
int regCkNull = 0;
int ii;
assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
sqlite3VdbeAddOp2(v, OP_IsNull, r1, destIfNull); VdbeCoverage(v);
if( destIfNull!=destIfFalse ){
regCkNull = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_Integer, 0, regCkNull);
}
for(ii=0; ii<pList->nExpr; ii++){
r2 = sqlite3ExprCodeTemp(pParse, pList->a[ii].pExpr, &regToFree);
if( regCkNull ){
sqlite3VdbeAddOp3(v, OP_BitAnd, regCkNull, r2, regCkNull);
}
if( ii<pList->nExpr-1 || destIfNull!=destIfFalse ){
sqlite3VdbeAddOp4(v, OP_Eq, r1, labelOk, r2,
(void*)pColl, P4_COLLSEQ); VdbeCoverage(v);
sqlite3VdbeChangeP5(v, affinity);
}else{
assert( destIfNull==destIfFalse );
sqlite3VdbeAddOp4(v, OP_Ne, r1, destIfFalse, r2,
(void*)pColl, P4_COLLSEQ); VdbeCoverage(v);
sqlite3VdbeChangeP5(v, affinity | SQLITE_JUMPIFNULL);
}
sqlite3ReleaseTempReg(pParse, regToFree);
}
if( regCkNull ){
sqlite3VdbeAddOp2(v, OP_IsNull, regCkNull, destIfNull); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
}
sqlite3VdbeResolveLabel(v, labelOk);
sqlite3ReleaseTempReg(pParse, regCkNull);
}else{
int addr1 = sqlite3VdbeAddOp1(v, OP_NotNull, r1); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Rewind, pExpr->iTable, destIfFalse);
VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfNull);
sqlite3VdbeJumpHere(v, addr1);
}
if( eType==IN_INDEX_ROWID ){
/* In this case, the RHS is the ROWID of table b-tree
/* If the LHS is NULL, then the result is either false or NULL depending
** on whether the RHS is empty or not, respectively.
*/
sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, destIfFalse); VdbeCoverage(v);
sqlite3VdbeAddOp3(v, OP_NotExists, pExpr->iTable, destIfFalse, r1);
VdbeCoverage(v);
}else{
/* In this case, the RHS is an index b-tree.
*/
sqlite3VdbeAddOp4(v, OP_Affinity, r1, 1, 0, &affinity, 1);
/* If the set membership test fails, then the result of the
** "x IN (...)" expression must be either 0 or NULL. If the set
** contains no NULL values, then the result is 0. If the set
** contains one or more NULL values, then the result of the
** expression is also NULL.
*/
assert( destIfFalse!=destIfNull || rRhsHasNull==0 );
if( rRhsHasNull==0 ){
/* This branch runs if it is known at compile time that the RHS
** cannot contain NULL values. This happens as the result
** of a "NOT NULL" constraint in the database schema.
**
** Also run this branch if NULL is equivalent to FALSE
** for this particular IN operator.
if( destIfNull==destIfFalse ){
/* Shortcut for the common case where the false and NULL outcomes are
** the same. */
sqlite3VdbeAddOp2(v, OP_IsNull, r1, destIfNull); VdbeCoverage(v);
}else{
int addr1 = sqlite3VdbeAddOp1(v, OP_NotNull, r1); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Rewind, pExpr->iTable, destIfFalse);
VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfNull);
sqlite3VdbeJumpHere(v, addr1);
}
if( eType==IN_INDEX_ROWID ){
/* In this case, the RHS is the ROWID of table b-tree
*/
sqlite3VdbeAddOp4Int(v, OP_NotFound, pExpr->iTable, destIfFalse, r1, 1);
sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, destIfFalse); VdbeCoverage(v);
sqlite3VdbeAddOp3(v, OP_NotExists, pExpr->iTable, destIfFalse, r1);
VdbeCoverage(v);
}else{
/* In this branch, the RHS of the IN might contain a NULL and
** the presence of a NULL on the RHS makes a difference in the
** outcome.
/* In this case, the RHS is an index b-tree.
*/
int j1;
/* First check to see if the LHS is contained in the RHS. If so,
** then the answer is TRUE the presence of NULLs in the RHS does
** not matter. If the LHS is not contained in the RHS, then the
** answer is NULL if the RHS contains NULLs and the answer is
** FALSE if the RHS is NULL-free.
sqlite3VdbeAddOp4(v, OP_Affinity, r1, 1, 0, &affinity, 1);
/* If the set membership test fails, then the result of the
** "x IN (...)" expression must be either 0 or NULL. If the set
** contains no NULL values, then the result is 0. If the set
** contains one or more NULL values, then the result of the
** expression is also NULL.
*/
j1 = sqlite3VdbeAddOp4Int(v, OP_Found, pExpr->iTable, 0, r1, 1);
VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_IsNull, rRhsHasNull, destIfNull);
VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
sqlite3VdbeJumpHere(v, j1);
assert( destIfFalse!=destIfNull || rRhsHasNull==0 );
if( rRhsHasNull==0 ){
/* This branch runs if it is known at compile time that the RHS
** cannot contain NULL values. This happens as the result
** of a "NOT NULL" constraint in the database schema.
**
** Also run this branch if NULL is equivalent to FALSE
** for this particular IN operator.
*/
sqlite3VdbeAddOp4Int(v, OP_NotFound, pExpr->iTable, destIfFalse, r1, 1);
VdbeCoverage(v);
}else{
/* In this branch, the RHS of the IN might contain a NULL and
** the presence of a NULL on the RHS makes a difference in the
** outcome.
*/
int j1;
/* First check to see if the LHS is contained in the RHS. If so,
** then the answer is TRUE the presence of NULLs in the RHS does
** not matter. If the LHS is not contained in the RHS, then the
** answer is NULL if the RHS contains NULLs and the answer is
** FALSE if the RHS is NULL-free.
*/
j1 = sqlite3VdbeAddOp4Int(v, OP_Found, pExpr->iTable, 0, r1, 1);
VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_IsNull, rRhsHasNull, destIfNull);
VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
sqlite3VdbeJumpHere(v, j1);
}
}
}
sqlite3ReleaseTempReg(pParse, r1);